CA1243118A - Aircraft terrain closure warning system with descent rate based envelope modification - Google Patents
Aircraft terrain closure warning system with descent rate based envelope modificationInfo
- Publication number
- CA1243118A CA1243118A CA000498124A CA498124A CA1243118A CA 1243118 A CA1243118 A CA 1243118A CA 000498124 A CA000498124 A CA 000498124A CA 498124 A CA498124 A CA 498124A CA 1243118 A CA1243118 A CA 1243118A
- Authority
- CA
- Canada
- Prior art keywords
- rate
- aircraft
- recited
- warning system
- descent
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C5/00—Measuring height; Measuring distances transverse to line of sight; Levelling between separated points; Surveyors' levels
- G01C5/005—Measuring height; Measuring distances transverse to line of sight; Levelling between separated points; Surveyors' levels altimeters for aircraft
Landscapes
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- General Physics & Mathematics (AREA)
- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- Emergency Alarm Devices (AREA)
Abstract
AIRCRAFT TERRAIN CLOSURE WARNING SYSTEM
WITH DESCENT RATE BASED ENVELOPE MODIFICATION
Abstract of the Disclosure Aircraft ground proximity warning systems that provide the pilot with a warning in the event that the closure rate with terrain is too high have the problem that when such systems are used in air-craft that are intentionally flown at high descent rates, such as occur in dives, nuisance warnings can occur. In order to minimize the problem, the criteria necessary to generate a terrain closure warning are modified as a function of the descent rate of the aircraft (12, 14, 30, 40, 42, 44) to prevent the closure rates encountered as a result of high descent rates from generating nuisance warnings.
WITH DESCENT RATE BASED ENVELOPE MODIFICATION
Abstract of the Disclosure Aircraft ground proximity warning systems that provide the pilot with a warning in the event that the closure rate with terrain is too high have the problem that when such systems are used in air-craft that are intentionally flown at high descent rates, such as occur in dives, nuisance warnings can occur. In order to minimize the problem, the criteria necessary to generate a terrain closure warning are modified as a function of the descent rate of the aircraft (12, 14, 30, 40, 42, 44) to prevent the closure rates encountered as a result of high descent rates from generating nuisance warnings.
Description
~243118 ~YL~aL~
Field of the Invention This invention relates generally to ground proximity warning systems for aircraft, and more par-ticularly to systems that monitor the altitude a~ove ground ~nd the closure rate of the aircraft to deter-mine a hazardous flight condition. Even more par-ticularly, the present invention relates to a system that warns the pilot of excessive terrain closure wherein the warning criteria are modified as a func-tion of the descent rate of the aircraft to prevent lS warnings from ~eing generated when the closure rate is the result of an intentional high descent rate such as that encountered during a dive or other abrupt maneuver.
PescriPtion of the Prior Art Ground proximity warning systems that warn of a dangerous flight condition are known. Examples of such sys~ems are disclosed in United States Patent Nos. 3,934,221; 3,934,222; 30944,968; 3,946,358 3,95~,218 and 3,95~,21Y assigned to the assignee of the present invention. All of these systems monitor the radio altitude and the radio altitude closure rate and generate a warning if the rate of closure is excessive for the altitude at which the aircraft is flying.
3L2fl~
--2~
While these systems do provide a way to warn a pilot of a hazardous condition resulting from an excessive closure rate with terrain, these systems are designed for use in transport aircraft, and not for highly maneuverable, high performance tactical aircraft such as the Lockheed S3-A whose flight and operational characteristics are such that high descent rates are often encountered in normal operation. Such high descent rates can result in sufficiently high clo-sure rates to cause systems designed for transport air-craft to generate false or nuisance warnings during cer-tain normal operational conditions of such an aircraft.
' ~
Accordingly, it i~ an object of the present invention to provide a ground proximity warning system ~hat overcomes many of the disadvantages of the prior art warning ~ystems when applied to maneuverable aircraft.
It is another o~ject of the present invention to provide an excessive terrain closure warning system that is particularly ~uitable for use in maneuvera~le, high performance aircraft.
It is yet another object of the present invention to provide an excessive closure rate warning system wherein the criteria for generating an exces-sive closure rate warning are modified as a functionof the descent rate of the aircraft.
The operational and flight conditions of a high performance aircraft, for example, tactical aircraft such as the Loc~heed S3-A, are considerably different than those of transport aircraft. For example, it is quite common for such an aircraft to engage in maneuvers wherein high descent rates are encountered.
Such high descent rates can result in sufficiently high closure rates to cause an excessive closure rate warning to ~e generated when such a warning is inap-~3~
--3~
propriate. It is possible to prevent such nuisancewarnings from being generated ~y altering the warning criteria such that the closure rates resulting from such normally encountered descent rates are insuffi-cient to cause a warning to ~e generated. However,such an approach will cause the terrain closure warn-ing system to ~ecome less sensitive and reduce the warning time provided under conditions where the ter-rain closure rate is, in fact, excessive.
Therefore, in accordance with a preferred em~odiment of the invention, there is provided a system that monitors the descent rate of the aircraft as well as the closure rate, and modifies the warning criteria necessary to generate an excessive closure rate warning as a function of descent rate in order to reduce the probability of generating a nuisance excessive terrain closure warning when the terrain closure is the result ~f a high descent rate that is part of an intentional maneuver. Furthermore, this system is implemented in such a way as to preserve terrain closure rate protection for flight path scenarios normally associated with controlled flight into terrain accidents.
DESCRIPTION OF THE DRAWING
These and other objects and advantages of the present invention will become readily apparent upon consideration of the following detailed descrip-tion and attached drawing, wherein:
FIG. 1 is a logical ~loc~ diagram of the warning system according to the invention;
FIG. 2 is a graph illustrating the closure rates necessary to generate a warning when the air-craft is flying with its flaps re~racted;
FIG. 3 is a graph illustrating the closure rates necessary to generate a warring when the aircraft ~Z~3~1~
is flying with its flaps extended or flying in a tactical mode of operation; and FIGS. 4 and 5 are tables illustrating how the limiter rate limits and filter time constants are esta~lished.
Referring now to the drawing, with particular attention to FIG. 1, there is illustrated an embodiment of the excessive terrain closure warning system gener-ally designated ~y the reference numeral 10. Thesystem 10 according to the invention is illustrated in FIG. 1 in logical ~10CK diagram form as a series of gates, comparators, summing junctions, limiters, filters, ccaling circuits and the like for purposes of illustration; however, it should ~e understood that the actual implementation of the loglc can be other than as shown in FIG. 1, with various digital and analog $mplementations being possible. The signals used ~y the system as described include radio altitude, radio altitude rate and barometric altitude rate and airspeed along with signals representative of flap position, landing gear position, mission mode selec-tion and whether there is weight on the wheels of the aircraft. Depending on the type of aircraft in which the warning system is installed, the signals for the ~y~tem shown in FIG. 1 can ~e obtained from indivi-dual instruments, such as a barometric altimeter 12, a barometric rate circuit 14, a radio altimeter 16, a radio rate circuit 26, a pilot/static ~ased airspeed 17 and discrete circuits indicative of flap position, landing gear position, mission mode selection and whether or not there is weight on the wheels. Such discretes include a flap up discrete 18, a gear up discrete 20, a mission selection switch 21 and a no weight on wheels discrete 22 in FIG. 1. Alternatively, ~2~3118 the barometric altitude and rate signals can be obtained from an air data computer, or the Z-velocity signal from an inertial navigation system can be used in place of the ~arometric rate signal.
Also, the signals can ~e obtained from a digital data bu- in certain newer aircraft.
The system according to the invention com-pares the altitude above ground of the aircraft with the closure rate, preferably radio altitude rate, or a computed closure rate ~ased on a com~ination of the radio altitude rate and the barometric altitude rate.
If the closure rate is excessive for the altitude at which the aircraft is flying, a warning is generated.
The determination of whether or not a warning is to ~e generated is made by a mode comparator 24 which compares tbe radio altitude signal from the radio altimeter 16 with a closure rate signal received from a rate circuit 26 via limiting and filtering circuitry 28 and a pair of summing junctions 30 and 32. The comparator 24 compares the closure rate signal and the radio altitude signal and cau~es a warning to be generated when the closure rate is excessive for the altitude at which the aircraft is flying. Preferably, the warning generated i8 an aural warning such as a ~TERRAIN" warning generated ~y a terrain warning generator 34 or a "PULL UP~ warning generated by a pull up warning generator 36 and applied either direct-ly or indirectly to a transducer 38 which may be a loudspea~er or a set of headphones.
As previously discussed, the system according to the invention modifies the warning criteria required for a warning to ~e generated in order to compensate for closure rates resulting from high descent rates.
The modification is accomplished ~y a summing junction 3S 40, a limiter 42, a scaling circuit 44 and the summing ~Z~3~
junction 30 which ~erve to bias the radio rate signal from the rate circuit 26 to provide a biased closure rate signal that $s applied to the limiting and fil-tering circuitry 2~.
In the embodiment illustrated in the FIG.
1, the limiting and filtering circuit includes a pair of low pass filters 46 and 4~, a high pass filter 50, a pair of limiters 52 and 54 and a summing junction 56. The filters 4~ and 50 cooperate with a summing junction 56 to provide a complementary filter of the type disclosed in the previously mentioned patents.
A series of gates 5~, 60 and 62 as well as comparators 64 and 66 cooperate with the flap up, gear up and no weight on wheels discretes 18, 20 and 22, respectively, to enable the sys~em only under certain conditions wbich will be discussed in a subsequent portion of ~
the specification. A delay circuit 6~ serves to reduce nuisance warnings that might occur immediately after take off ~loss of WOW signal) due to barometric ground effects, and another delay circuit 70 delays the gener-ation of the ~PULL UP~ warning until two repetitions of the ~TERRAIN" warning have occurred. A scaling circuit 72, a summing junction 74, a limiter 76 and a comparator 7~ serve to provide a less than 200 foot signal that is used to alter the limits of the limiters 52 and 54, and hence the warning criteria as a function of barometric rate in a conventional fashion.
In operation, the rate signal from the limiting and filtering circuit 2~ is modified ~y scaling circuit ~0 and summing junction 32. These functions serve to implement the slope and offset observed in the warning envelopes of FIGS. 2 and 3.
The comparator 24 compares the signal from the summing junction 32 with the output of the radio altimeter 16 and causes either the warning generator 34 or the ~Z~31 1~3 warning generator 36 to generate a warning whenever the closure rate is excessive for the altitude above ground at which the aircraft is flying.
As previously stated, the summing junction 40, the limiter 42 and the scaling circuit 44 serve to com~ine a signal representative of the descent rate of the aircraft with the signal from the rate circuit 26. Thus, the scaled descent rate from the scaling circuit 44 is subtracted from the output of the rate circuit 26 ~y the summing junction 30 in order to cancel out a portion of the closure rate signal prior to limiting and filtering. Also, the summing junction 40 ~erves to su~ract a signal repre-sentative of a 2000 feet per minute descent rate from the output of the ra~e circuit 14 ~o that no ~iasing of the clo~ure rate siynal can occur unles-~ the descent rate exceeds 2000 feet per minute. The limiter 42 permits signals representative of descent rates greater than 2000 feet per minute to be applied from the summing junction 40 to the scaling circuit 44 but limits any signals representative of descent rates les~ than 2000 feet per minute or ascent rates.
The modification to the warning criteria is illustrated in graphical form in FIG. 2. As is illus-trated in FIG. 2 when the aircraft is flying with its flap~ retracted, a warning is generated whenever the closure rate exceeds the rate defined by a line 100.
If the speed of the aircraft is 214 knots or less, the warning is generated only between altitudes 30 feet and 1650 feet. With increasing airspeed, the upper altitude limit is increased until the warning may ~e generated at altitudes as high as 2450 feet at airspeeds in exces6 of 275 ~nots. Thus, the line 100 together with the upper and lower altitude limits define the warning criteria when the barometric descent ~Z431~
rate i~ 2000 feet per minute or less.
The biased closure rate signal applied by the summing junction 30 to the limiting and filtering circuitry 2~ can be defined by the equation:
BCR = C~ - lKtDR-A fpm)]
wherein BCR is the biased closure rate, CR is the unmodified closure rate or radio rate DR is the descent rate (barometric descent rate or Z-velocity) and K
and A are constants. Because of the action of the limiting circuit 42, the term in brac~ets remains zero until the descent rate exceeds 2000 feet per minute. Thus, the value for A in the equation for the ~iased closure rate in the illustrated embodiment would ~e 2000 feet per minute. Consequently, the lS warning criteria are defined by the line 100 for descent rates of less than 2000 feet per minute.
However, at higher descent rates, the warning boundary is effectively shifted to the right as a function of descent ra~e. The amount t.hat the boundary is shifted at a particular descent rate, depends on whether the landing gear of the aircraft is up or down. With the landing gear down, the scaling factor R is selected to ~e 0.75. With the landin~ gear up, greater descent rates may be tolerated, and the scaling factor K is increased to 1.5, shifting the warning boundary more to the ~ight.
FIG. 3 illustrates the criteria required for a warning to be generated when the aircraft is flying with its flaps extended or when the aircraft is flying in a tactical mode, such as, for example, in a low level reconnaissance mode or in an attack mode. A tactical mode of operation is indicated to the system when the pilot actuates a mission ~elect switch in the cockpit of the aircraft.
The warning envelope illustrated in FIG. 3 illustrates the warning criteria when the descent ~Z~3~
g rate of the aircraft is less than 2000 feet per minute.
In sucn an event, the left hand warning ~oundary is defined ~y a line 102. Tbe upper warning ~oundary is defined by a line 104 at 789 feet of radio altitude S and the lower warning boundary is defined by a line 106. The warning boundary 106 i movable as a func-tion ~arometric descent rate and is selected to be 200 feet of radio altitude at descent rates less than 400 feet per minute. For greater descent rates, the lower boundary 106 is raised until it reaches 600 feet of radio altitude for descent rates of l000 feet per minute and more. Two distinct warnings are given.
Above 550 feet of radio altitude tbe warning is ~TERRAIN-PULL UP". Below 550 feet sf radio altitude, the warn-ing is simply "TERRAIN" if the landing gear is down and the flaps are extended. Otherwise the entire ~TERRRIN-PULL UP" message is generated. As in the case of the envelope illustrated in FIG. 2, the warn-ing ~oundary 102 i~ shifted to the right as a function of descent rate, with the shifting function being the same as the function described in conjunction with FIG. 2.
As previously stated, the shapes of the warning criteria are altered as a function airspeed and landing gear and flap position. Such alteration iB accompli hed by altering the rate limits of the rate limiters 52 and 54 and the time constants Tl and T2 f the filters 46, 48 and 50 ~FIG. 1). The time constant Tl, as sampled at the output of the filter 46, is varied as a function of closure rate. If the rate is between the limits A and B of the limiter 54, the time constant Tl is set to 0.1 second. If the rate is outside of the limits A and B, the time con-stant is increased to 3.0 seconds. This rate limit-ing and filtering results in effectively ~sticking"
31 2~-~3~
the clo~ure at the limit values for ~hort persons of time, thereby providing ~etter nuisance warning margins ~or erratic radio alti~ude signals.
The conditions for setting the rate limits A and B are illustrated in FIG. 4. If the flaps are up and the sircraft is above 30 feet of radio altitude, and there is no weight on the wheels and if the air-craft is flying at less than 214 knots with mission select not active, A is set to 2000 feet per minute and B i 6et to 40~0 feet per minute as i~ indicated by relation (1). At ~75 knots or greater, the rate limit B i8 cet to 5100 feet per minute aB i5 indicated by relation ~2). ~etween airspeeds of 214 ~nots and Z75 Knots, the rate limit ~ is increaRed linearly ~s defined ~y the equation defining the rate limit ~ in FIG. 4, The relation~ (1) and ~2~ correspond to the airspeed expansion above 214 ~nots illu~tra~ed in FIG. 2. The rate limits A and B required to produce the warning envelope of FIG. 3 are illustrated ~y relations (3) and (4) of FIG. 4. If the aircraft is flying ~bove 200 feet of radio alt$tude and the flaps are down or the mission ~elect ~witch has been acti-vated, the rate limits A and B ~re 910 and 3000 feet per ~inute, respectively. With the flaps down and if the aircraft i5 either flying ~elow 200 feet or there i8 weight on the wheels, the rate limit8 are ~et at -590 and 1500 feet per minute, re~pectively, to inhi~it all functions.
Similarly, the time constant T2 is also adjusted as a function of airspeed, altitude, flap position, weight on wheels and whether a mission has been ~elected as is illustrated in FIG. 4. The gear up latched (GUL) and gear down latched (GDL) signals are logic signals that are available from a conventional ground proximity warning system. The time constant i 311~
adju~ted to higher values as the pro~ability of ~omentary excursions into the envel.opes or FIGS. 2 and 3 increases, tbereby providing additional m~rgin against nuisance warnings. Such excurs~on~ are ~ore S li~ely when the aircraft is in landing configuration on ~inal approacb or in a mission select ~ode.
O~viously, many modi~ications and var~ations of the present invention are po~si~le in light of the ~ove teachings. Thus, it is to be understood that, within ~he scope o~ the appended claims, the lnvention may be pract~ced otherwise than as speciically descri~ed above.
Field of the Invention This invention relates generally to ground proximity warning systems for aircraft, and more par-ticularly to systems that monitor the altitude a~ove ground ~nd the closure rate of the aircraft to deter-mine a hazardous flight condition. Even more par-ticularly, the present invention relates to a system that warns the pilot of excessive terrain closure wherein the warning criteria are modified as a func-tion of the descent rate of the aircraft to prevent lS warnings from ~eing generated when the closure rate is the result of an intentional high descent rate such as that encountered during a dive or other abrupt maneuver.
PescriPtion of the Prior Art Ground proximity warning systems that warn of a dangerous flight condition are known. Examples of such sys~ems are disclosed in United States Patent Nos. 3,934,221; 3,934,222; 30944,968; 3,946,358 3,95~,218 and 3,95~,21Y assigned to the assignee of the present invention. All of these systems monitor the radio altitude and the radio altitude closure rate and generate a warning if the rate of closure is excessive for the altitude at which the aircraft is flying.
3L2fl~
--2~
While these systems do provide a way to warn a pilot of a hazardous condition resulting from an excessive closure rate with terrain, these systems are designed for use in transport aircraft, and not for highly maneuverable, high performance tactical aircraft such as the Lockheed S3-A whose flight and operational characteristics are such that high descent rates are often encountered in normal operation. Such high descent rates can result in sufficiently high clo-sure rates to cause systems designed for transport air-craft to generate false or nuisance warnings during cer-tain normal operational conditions of such an aircraft.
' ~
Accordingly, it i~ an object of the present invention to provide a ground proximity warning system ~hat overcomes many of the disadvantages of the prior art warning ~ystems when applied to maneuverable aircraft.
It is another o~ject of the present invention to provide an excessive terrain closure warning system that is particularly ~uitable for use in maneuvera~le, high performance aircraft.
It is yet another object of the present invention to provide an excessive closure rate warning system wherein the criteria for generating an exces-sive closure rate warning are modified as a functionof the descent rate of the aircraft.
The operational and flight conditions of a high performance aircraft, for example, tactical aircraft such as the Loc~heed S3-A, are considerably different than those of transport aircraft. For example, it is quite common for such an aircraft to engage in maneuvers wherein high descent rates are encountered.
Such high descent rates can result in sufficiently high closure rates to cause an excessive closure rate warning to ~e generated when such a warning is inap-~3~
--3~
propriate. It is possible to prevent such nuisancewarnings from being generated ~y altering the warning criteria such that the closure rates resulting from such normally encountered descent rates are insuffi-cient to cause a warning to ~e generated. However,such an approach will cause the terrain closure warn-ing system to ~ecome less sensitive and reduce the warning time provided under conditions where the ter-rain closure rate is, in fact, excessive.
Therefore, in accordance with a preferred em~odiment of the invention, there is provided a system that monitors the descent rate of the aircraft as well as the closure rate, and modifies the warning criteria necessary to generate an excessive closure rate warning as a function of descent rate in order to reduce the probability of generating a nuisance excessive terrain closure warning when the terrain closure is the result ~f a high descent rate that is part of an intentional maneuver. Furthermore, this system is implemented in such a way as to preserve terrain closure rate protection for flight path scenarios normally associated with controlled flight into terrain accidents.
DESCRIPTION OF THE DRAWING
These and other objects and advantages of the present invention will become readily apparent upon consideration of the following detailed descrip-tion and attached drawing, wherein:
FIG. 1 is a logical ~loc~ diagram of the warning system according to the invention;
FIG. 2 is a graph illustrating the closure rates necessary to generate a warning when the air-craft is flying with its flaps re~racted;
FIG. 3 is a graph illustrating the closure rates necessary to generate a warring when the aircraft ~Z~3~1~
is flying with its flaps extended or flying in a tactical mode of operation; and FIGS. 4 and 5 are tables illustrating how the limiter rate limits and filter time constants are esta~lished.
Referring now to the drawing, with particular attention to FIG. 1, there is illustrated an embodiment of the excessive terrain closure warning system gener-ally designated ~y the reference numeral 10. Thesystem 10 according to the invention is illustrated in FIG. 1 in logical ~10CK diagram form as a series of gates, comparators, summing junctions, limiters, filters, ccaling circuits and the like for purposes of illustration; however, it should ~e understood that the actual implementation of the loglc can be other than as shown in FIG. 1, with various digital and analog $mplementations being possible. The signals used ~y the system as described include radio altitude, radio altitude rate and barometric altitude rate and airspeed along with signals representative of flap position, landing gear position, mission mode selec-tion and whether there is weight on the wheels of the aircraft. Depending on the type of aircraft in which the warning system is installed, the signals for the ~y~tem shown in FIG. 1 can ~e obtained from indivi-dual instruments, such as a barometric altimeter 12, a barometric rate circuit 14, a radio altimeter 16, a radio rate circuit 26, a pilot/static ~ased airspeed 17 and discrete circuits indicative of flap position, landing gear position, mission mode selection and whether or not there is weight on the wheels. Such discretes include a flap up discrete 18, a gear up discrete 20, a mission selection switch 21 and a no weight on wheels discrete 22 in FIG. 1. Alternatively, ~2~3118 the barometric altitude and rate signals can be obtained from an air data computer, or the Z-velocity signal from an inertial navigation system can be used in place of the ~arometric rate signal.
Also, the signals can ~e obtained from a digital data bu- in certain newer aircraft.
The system according to the invention com-pares the altitude above ground of the aircraft with the closure rate, preferably radio altitude rate, or a computed closure rate ~ased on a com~ination of the radio altitude rate and the barometric altitude rate.
If the closure rate is excessive for the altitude at which the aircraft is flying, a warning is generated.
The determination of whether or not a warning is to ~e generated is made by a mode comparator 24 which compares tbe radio altitude signal from the radio altimeter 16 with a closure rate signal received from a rate circuit 26 via limiting and filtering circuitry 28 and a pair of summing junctions 30 and 32. The comparator 24 compares the closure rate signal and the radio altitude signal and cau~es a warning to be generated when the closure rate is excessive for the altitude at which the aircraft is flying. Preferably, the warning generated i8 an aural warning such as a ~TERRAIN" warning generated ~y a terrain warning generator 34 or a "PULL UP~ warning generated by a pull up warning generator 36 and applied either direct-ly or indirectly to a transducer 38 which may be a loudspea~er or a set of headphones.
As previously discussed, the system according to the invention modifies the warning criteria required for a warning to ~e generated in order to compensate for closure rates resulting from high descent rates.
The modification is accomplished ~y a summing junction 3S 40, a limiter 42, a scaling circuit 44 and the summing ~Z~3~
junction 30 which ~erve to bias the radio rate signal from the rate circuit 26 to provide a biased closure rate signal that $s applied to the limiting and fil-tering circuitry 2~.
In the embodiment illustrated in the FIG.
1, the limiting and filtering circuit includes a pair of low pass filters 46 and 4~, a high pass filter 50, a pair of limiters 52 and 54 and a summing junction 56. The filters 4~ and 50 cooperate with a summing junction 56 to provide a complementary filter of the type disclosed in the previously mentioned patents.
A series of gates 5~, 60 and 62 as well as comparators 64 and 66 cooperate with the flap up, gear up and no weight on wheels discretes 18, 20 and 22, respectively, to enable the sys~em only under certain conditions wbich will be discussed in a subsequent portion of ~
the specification. A delay circuit 6~ serves to reduce nuisance warnings that might occur immediately after take off ~loss of WOW signal) due to barometric ground effects, and another delay circuit 70 delays the gener-ation of the ~PULL UP~ warning until two repetitions of the ~TERRAIN" warning have occurred. A scaling circuit 72, a summing junction 74, a limiter 76 and a comparator 7~ serve to provide a less than 200 foot signal that is used to alter the limits of the limiters 52 and 54, and hence the warning criteria as a function of barometric rate in a conventional fashion.
In operation, the rate signal from the limiting and filtering circuit 2~ is modified ~y scaling circuit ~0 and summing junction 32. These functions serve to implement the slope and offset observed in the warning envelopes of FIGS. 2 and 3.
The comparator 24 compares the signal from the summing junction 32 with the output of the radio altimeter 16 and causes either the warning generator 34 or the ~Z~31 1~3 warning generator 36 to generate a warning whenever the closure rate is excessive for the altitude above ground at which the aircraft is flying.
As previously stated, the summing junction 40, the limiter 42 and the scaling circuit 44 serve to com~ine a signal representative of the descent rate of the aircraft with the signal from the rate circuit 26. Thus, the scaled descent rate from the scaling circuit 44 is subtracted from the output of the rate circuit 26 ~y the summing junction 30 in order to cancel out a portion of the closure rate signal prior to limiting and filtering. Also, the summing junction 40 ~erves to su~ract a signal repre-sentative of a 2000 feet per minute descent rate from the output of the ra~e circuit 14 ~o that no ~iasing of the clo~ure rate siynal can occur unles-~ the descent rate exceeds 2000 feet per minute. The limiter 42 permits signals representative of descent rates greater than 2000 feet per minute to be applied from the summing junction 40 to the scaling circuit 44 but limits any signals representative of descent rates les~ than 2000 feet per minute or ascent rates.
The modification to the warning criteria is illustrated in graphical form in FIG. 2. As is illus-trated in FIG. 2 when the aircraft is flying with its flap~ retracted, a warning is generated whenever the closure rate exceeds the rate defined by a line 100.
If the speed of the aircraft is 214 knots or less, the warning is generated only between altitudes 30 feet and 1650 feet. With increasing airspeed, the upper altitude limit is increased until the warning may ~e generated at altitudes as high as 2450 feet at airspeeds in exces6 of 275 ~nots. Thus, the line 100 together with the upper and lower altitude limits define the warning criteria when the barometric descent ~Z431~
rate i~ 2000 feet per minute or less.
The biased closure rate signal applied by the summing junction 30 to the limiting and filtering circuitry 2~ can be defined by the equation:
BCR = C~ - lKtDR-A fpm)]
wherein BCR is the biased closure rate, CR is the unmodified closure rate or radio rate DR is the descent rate (barometric descent rate or Z-velocity) and K
and A are constants. Because of the action of the limiting circuit 42, the term in brac~ets remains zero until the descent rate exceeds 2000 feet per minute. Thus, the value for A in the equation for the ~iased closure rate in the illustrated embodiment would ~e 2000 feet per minute. Consequently, the lS warning criteria are defined by the line 100 for descent rates of less than 2000 feet per minute.
However, at higher descent rates, the warning boundary is effectively shifted to the right as a function of descent ra~e. The amount t.hat the boundary is shifted at a particular descent rate, depends on whether the landing gear of the aircraft is up or down. With the landing gear down, the scaling factor R is selected to ~e 0.75. With the landin~ gear up, greater descent rates may be tolerated, and the scaling factor K is increased to 1.5, shifting the warning boundary more to the ~ight.
FIG. 3 illustrates the criteria required for a warning to be generated when the aircraft is flying with its flaps extended or when the aircraft is flying in a tactical mode, such as, for example, in a low level reconnaissance mode or in an attack mode. A tactical mode of operation is indicated to the system when the pilot actuates a mission ~elect switch in the cockpit of the aircraft.
The warning envelope illustrated in FIG. 3 illustrates the warning criteria when the descent ~Z~3~
g rate of the aircraft is less than 2000 feet per minute.
In sucn an event, the left hand warning ~oundary is defined ~y a line 102. Tbe upper warning ~oundary is defined by a line 104 at 789 feet of radio altitude S and the lower warning boundary is defined by a line 106. The warning boundary 106 i movable as a func-tion ~arometric descent rate and is selected to be 200 feet of radio altitude at descent rates less than 400 feet per minute. For greater descent rates, the lower boundary 106 is raised until it reaches 600 feet of radio altitude for descent rates of l000 feet per minute and more. Two distinct warnings are given.
Above 550 feet of radio altitude tbe warning is ~TERRAIN-PULL UP". Below 550 feet sf radio altitude, the warn-ing is simply "TERRAIN" if the landing gear is down and the flaps are extended. Otherwise the entire ~TERRRIN-PULL UP" message is generated. As in the case of the envelope illustrated in FIG. 2, the warn-ing ~oundary 102 i~ shifted to the right as a function of descent rate, with the shifting function being the same as the function described in conjunction with FIG. 2.
As previously stated, the shapes of the warning criteria are altered as a function airspeed and landing gear and flap position. Such alteration iB accompli hed by altering the rate limits of the rate limiters 52 and 54 and the time constants Tl and T2 f the filters 46, 48 and 50 ~FIG. 1). The time constant Tl, as sampled at the output of the filter 46, is varied as a function of closure rate. If the rate is between the limits A and B of the limiter 54, the time constant Tl is set to 0.1 second. If the rate is outside of the limits A and B, the time con-stant is increased to 3.0 seconds. This rate limit-ing and filtering results in effectively ~sticking"
31 2~-~3~
the clo~ure at the limit values for ~hort persons of time, thereby providing ~etter nuisance warning margins ~or erratic radio alti~ude signals.
The conditions for setting the rate limits A and B are illustrated in FIG. 4. If the flaps are up and the sircraft is above 30 feet of radio altitude, and there is no weight on the wheels and if the air-craft is flying at less than 214 knots with mission select not active, A is set to 2000 feet per minute and B i 6et to 40~0 feet per minute as i~ indicated by relation (1). At ~75 knots or greater, the rate limit B i8 cet to 5100 feet per minute aB i5 indicated by relation ~2). ~etween airspeeds of 214 ~nots and Z75 Knots, the rate limit ~ is increaRed linearly ~s defined ~y the equation defining the rate limit ~ in FIG. 4, The relation~ (1) and ~2~ correspond to the airspeed expansion above 214 ~nots illu~tra~ed in FIG. 2. The rate limits A and B required to produce the warning envelope of FIG. 3 are illustrated ~y relations (3) and (4) of FIG. 4. If the aircraft is flying ~bove 200 feet of radio alt$tude and the flaps are down or the mission ~elect ~witch has been acti-vated, the rate limits A and B ~re 910 and 3000 feet per ~inute, respectively. With the flaps down and if the aircraft i5 either flying ~elow 200 feet or there i8 weight on the wheels, the rate limit8 are ~et at -590 and 1500 feet per minute, re~pectively, to inhi~it all functions.
Similarly, the time constant T2 is also adjusted as a function of airspeed, altitude, flap position, weight on wheels and whether a mission has been ~elected as is illustrated in FIG. 4. The gear up latched (GUL) and gear down latched (GDL) signals are logic signals that are available from a conventional ground proximity warning system. The time constant i 311~
adju~ted to higher values as the pro~ability of ~omentary excursions into the envel.opes or FIGS. 2 and 3 increases, tbereby providing additional m~rgin against nuisance warnings. Such excurs~on~ are ~ore S li~ely when the aircraft is in landing configuration on ~inal approacb or in a mission select ~ode.
O~viously, many modi~ications and var~ations of the present invention are po~si~le in light of the ~ove teachings. Thus, it is to be understood that, within ~he scope o~ the appended claims, the lnvention may be pract~ced otherwise than as speciically descri~ed above.
Claims (29)
1. A ground proximity warning system for an aircraft comprising:
means responsive to a signal representative of the altitude of the aircraft above ground and to a signal representative of the terrain closure rate of the aircraft for generating a warning when the terrain closure rate is excessive according to a predetermined set of criteria for the altitude at which the aircraft is flying;
means responsive to the descent rate of the aircraft for providing a signal representative of the descent rate of the aircraft; and means responsive to said descent rate signal for altering said predetermined set of criteria as a function of the descent rate.
means responsive to a signal representative of the altitude of the aircraft above ground and to a signal representative of the terrain closure rate of the aircraft for generating a warning when the terrain closure rate is excessive according to a predetermined set of criteria for the altitude at which the aircraft is flying;
means responsive to the descent rate of the aircraft for providing a signal representative of the descent rate of the aircraft; and means responsive to said descent rate signal for altering said predetermined set of criteria as a function of the descent rate.
2. A ground proximity warning system as recited in claim 1 wherein said predetermined criteria are altered to make the terrain closure rate generating means less sensitive to closure rate when the aircraft is descending.
3. A ground proximity warning system as recited in claim 2 wherein said altering means includes means for altering said criteria as a first function of descent rate when the landing gear of the aircraft is retracted and as a second function of descent rate when the landing gear is extended.
4. A ground proximity warning system as recited in claim 3 wherein said first function is operative to alter said criteria at a greater rate than said second function.
5. A ground proximity warning system as recited in claim 2 wherein said predetermined criteria are altered when the descent rate exceeds a predeter-mined descent rate.
6. A ground proximity warning system as recited in claim 5 wherein said predetermined descent rate is on the order of approximately 2000 feet per minute.
7. A ground proximity warning system for an aircraft comprising:
a source of signals representative of the altitude of the aircraft above ground;
a source of signals representative of the descent rate of the aircraft;
means for providing a signal representative of the terrain closure rate of the aircraft;
means responsive to the altitude above ground signal providing means and to the terrain closure rate signal providing means for generating a warning if the terrain closure rate is excessive according to a predetermined set of criteria for the altitude at which the aircraft is flying; and means responsive to said descent rate signal providing means for altering said predetermined set of criteria as a function of descent rate of the air-craft.
a source of signals representative of the altitude of the aircraft above ground;
a source of signals representative of the descent rate of the aircraft;
means for providing a signal representative of the terrain closure rate of the aircraft;
means responsive to the altitude above ground signal providing means and to the terrain closure rate signal providing means for generating a warning if the terrain closure rate is excessive according to a predetermined set of criteria for the altitude at which the aircraft is flying; and means responsive to said descent rate signal providing means for altering said predetermined set of criteria as a function of descent rate of the air-craft.
8. A ground proximity warning system as recited in claim 7 wherein said altering means is responsive to said descent rate signal providing means for altering said predetermined set of criteria only when the descent rate of the aircraft exceeds a pre-determined rate.
9. A ground proximity warning system as recited in claim 8 wherein said predetermined descent rate is on the order of approximately 2000 feet per minute.
10. A ground proximity warning system as recited in claim 7 wherein said predetermined criteria are altered to make the terrain closure rate generat-ing means less sensitive to closure rate when the aircraft is descending.
11. A ground proximity warning system as recited in claim 10 wherein said altering means in-cludes means for altering said criteria as a first function of descent rate when the landing gear of the aircraft is retracted and as a second function of descent rate when the landing gear is extended.
12. A ground proximity warning system as recited in claim 11 wherein said first function is operative to alter said criteria at a greater rate than said second function.
13. A ground proximity warning system for an aircraft comprising:
a source of signals representative of the altitude of the aircraft above ground;
a source of signals representative of the descent rate of the aircraft;
means for providing a signal representative of the terrain closure rate of the aircraft;
means for subtracting at least a portion of said descent rate signal from said closure rate signal to provide a biased closure rate signal; and means responsive to the altitude above ground signal providing means and to said subtracting means for generating a warning if the biased terrain closure rate of the aircraft is excessive for the altitude at which the aircraft is flying.
a source of signals representative of the altitude of the aircraft above ground;
a source of signals representative of the descent rate of the aircraft;
means for providing a signal representative of the terrain closure rate of the aircraft;
means for subtracting at least a portion of said descent rate signal from said closure rate signal to provide a biased closure rate signal; and means responsive to the altitude above ground signal providing means and to said subtracting means for generating a warning if the biased terrain closure rate of the aircraft is excessive for the altitude at which the aircraft is flying.
14. A ground proximity warning system as recited in claim 13 wherein said subtracting means is responsive to said descent rate signal only when the aircraft is descending.
15. A ground proximity warning system as recited in claim 14 wherein said subtracting means is responsive to said descent rate signal providing means only when the descent rate of the aircraft exceeds a predetermined rate.
16. A ground proximity warning system as recited in claim 15 wherein said predetermined descent rate is on the order of approximately 2000 feet per minute.
17. A ground proximity warning system as recited in claim 13 wherein the biased closure rate signal is defined by the following equation:
BCR = CR - [K(DR-A fpm)]
wherein BCR is the biased closure rate, CR is the unmodified closure rate, DR is the descent rate and R and A are constants.
BCR = CR - [K(DR-A fpm)]
wherein BCR is the biased closure rate, CR is the unmodified closure rate, DR is the descent rate and R and A are constants.
18. A ground proximity warning system as recited in claim 17 wherein K is on the order of 0.75 to 1.5.
19. A ground proximity warning system as recited in claim 18 further including means for pro-viding a signal representative of the position of the landing gear of the aircraft for altering the value of K from 1.5 when the landing gear is up to 0.75 when the landing gear is down.
20. A ground proximity warning system as recited in claim 17 wherein A is on the order of 2000.
21. In a ground proximity warning system for an aircraft of the type having means responsive to a signal representative of the altitude of the aircraft above ground and to a signal representative of the terrain closure rate of the aircraft for generating a warning when the closure rate is exces-sive the improvement comprising:
means responsive to the descent rate of the aircraft for biasing the closure rate signal as a function of descent rate so that a higher closure rate is required to generate the warning when the aircraft is descending.
means responsive to the descent rate of the aircraft for biasing the closure rate signal as a function of descent rate so that a higher closure rate is required to generate the warning when the aircraft is descending.
22. The improvement recited in claim 21 wherein said biasing means is operative to bias the closure rate signal only when the aircraft is descend-ing.
23. The improvement recited in claim 22 wherein said-biasing means is operative to bias the closure rate signal only when the descent rate of the aircraft includes a predetermined rate.
24. The improvement recited in claim 23 wherein said predetermined descent rate is on the order of approximately 2000 feet per minute.
25. The improvement recited in claim 21 further including means responsive to the position of the landing gear for rendering said biasing means operative to bias the closure rate signal to a greater degree when the landing gear is up than when the land-ing gear is down.
26. The improvement recited in claim 21 wherein the biased closure rate signal is defined by the following equation:
BCR = CR - [K(DR-A fpm)]
wherein BCR is the biased closure rate, CR is the unmodified closure rate, DR is the descent rate and K and A are constants.
BCR = CR - [K(DR-A fpm)]
wherein BCR is the biased closure rate, CR is the unmodified closure rate, DR is the descent rate and K and A are constants.
27. The improvement recited in claim 26 wherein K is on the order of 0.75 to 1.5.
28. The improvement recited in claim 27 further including means for providing a signal repre-sentative of the position of the landing gear of the aircraft for altering the value of K from 1.5 when the landing gear is up to 0.75 when the landing gear is down.
29. A ground proximity warning system as recited in claim 26 wherein A is on the order of 2000.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US704,365 | 1976-07-12 | ||
| US70436585A | 1985-02-22 | 1985-02-22 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1243118A true CA1243118A (en) | 1988-10-11 |
Family
ID=24829167
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000498124A Expired CA1243118A (en) | 1985-02-22 | 1985-12-19 | Aircraft terrain closure warning system with descent rate based envelope modification |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US4792799A (en) |
| EP (1) | EP0217852B1 (en) |
| JP (1) | JPS62500264A (en) |
| CA (1) | CA1243118A (en) |
| DE (1) | DE3685790T2 (en) |
| FI (1) | FI864239A (en) |
| WO (1) | WO1986005023A1 (en) |
Families Citing this family (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5202684A (en) * | 1985-10-17 | 1993-04-13 | Toyo Communication Equipment Co., Ltd. | System of an aircraft collision avoidance system for suppressing useless alarms |
| US4916448A (en) * | 1988-02-26 | 1990-04-10 | The United States Of America As Represented By The Secretary Of The Air Force | Low altitude warning system for aircraft |
| US5136512A (en) * | 1988-06-26 | 1992-08-04 | Cubic Defense Systems, Inc. | Ground collision avoidance system |
| US5349347A (en) * | 1993-03-29 | 1994-09-20 | Alliedsignal Inc. | Method and apparatus for correcting dynamically induced errors in static pressure, airspeed and airspeed rate |
| US5428354A (en) * | 1993-11-05 | 1995-06-27 | Alliedsignal Inc. | Ground proximity warning system for non-retractable landing gear aircraft |
| SE9401847L (en) * | 1994-05-30 | 1995-05-22 | Saab Scania Ab | Method and apparatus for performing phase compensation in a vehicle control system |
| FR2728374A1 (en) * | 1994-12-15 | 1996-06-21 | Aerospatiale | METHOD AND APPARATUS FOR PROVIDING INFORMATION, ALERT, OR ALARM FOR AN AIRCRAFT NEAR THE GROUND |
| US5745053A (en) * | 1995-12-08 | 1998-04-28 | Fleming, Iii; Hoyt A. | Landing gear warning apparatus and method for pilots approaching a runway with retracted landing gear |
| US5781146A (en) * | 1996-03-11 | 1998-07-14 | Imaging Accessories, Inc. | Automatic horizontal and vertical scanning radar with terrain display |
| US5828332A (en) * | 1996-03-11 | 1998-10-27 | Imaging Accessories, Inc. | Automatic horizontal and vertical scanning radar with terrain display |
| US7386373B1 (en) * | 2003-01-07 | 2008-06-10 | Garmin International, Inc. | System, method and apparatus for searching geographic area using prioritized spatial order |
| US6745115B1 (en) | 2003-01-07 | 2004-06-01 | Garmin Ltd. | System, method and apparatus for searching geographic area using prioritized spacial order |
| US7382287B1 (en) | 2003-06-03 | 2008-06-03 | Garmin International, Inc | Avionics system, method and apparatus for selecting a runway |
| US6980892B1 (en) | 2003-11-18 | 2005-12-27 | Garmin International, Inc. | Avionics system and method for providing altitude alerts during final landing approach |
| US8624757B2 (en) * | 2011-06-27 | 2014-01-07 | General Electric Company | Method for visually indicating an advisory from the traffic collision avoidance system on a flight display |
| FR3036497B1 (en) * | 2015-05-19 | 2017-06-16 | Airbus Operations Sas | METHOD AND SYSTEM FOR DATA MANAGEMENT OF AN AIRCRAFT RADIOALTIMETER |
| US9751636B2 (en) | 2015-12-15 | 2017-09-05 | International Business Machines Corporation | Dynamic detection of landing gear deployment |
Family Cites Families (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3715718A (en) * | 1970-08-11 | 1973-02-06 | Sundstrand Data Control | Ground proximity warning system utilizing radio and barometric altimeter combination |
| US3946358A (en) * | 1974-06-19 | 1976-03-23 | Sundstrand Data Control, Inc. | Aircraft ground proximity warning instrument |
| US3958218A (en) * | 1974-10-03 | 1976-05-18 | Sundstrand Data Control, Inc. | Aircraft ground proximity warning system with speed compensation |
| US3944968A (en) * | 1974-11-01 | 1976-03-16 | Sundstrand Data Control, Inc. | Aircraft ground proximity warning system having speed versus altitude compensation |
| US3934221A (en) * | 1975-03-06 | 1976-01-20 | Sundstrand Data Control, Inc. | Terrain closure warning system with altitude rate signal conditioning |
| US3958219A (en) * | 1975-03-06 | 1976-05-18 | Sundstrand Data Control, Inc. | Terrain closure warning system with altitude rate signal conditioning |
| US3934222A (en) * | 1975-04-02 | 1976-01-20 | Sundstrand Data Control, Inc. | Terrain closure warning system with climb inhibit and altitude gain measurement |
| US4016565A (en) * | 1975-09-15 | 1977-04-05 | Rockwell International Corporation | Aircraft ground closure rate filtering method and means |
| US4060793A (en) * | 1976-07-19 | 1977-11-29 | Sundstrand Data Control, Inc. | Excessive sink rate warning system for aircraft |
| US4215334A (en) * | 1978-02-09 | 1980-07-29 | Sundstrand Data Control, Inc. | Aircraft excessive descent rate warning system |
| US4495483A (en) * | 1981-04-30 | 1985-01-22 | Sundstrand Corporation | Ground proximity warning system with time based mode switching |
| US4567483A (en) * | 1982-12-10 | 1986-01-28 | Sundstrand Data Control, Inc. | Position based ground proximity warning system for aircraft |
| CA1241082A (en) * | 1983-05-13 | 1988-08-23 | Everette E. Vermilion | Warning system for tactical aircraft |
| US4639730A (en) * | 1983-05-13 | 1987-01-27 | Sundstrand Data Control, Inc. | Excessive terrain closure warning system |
| US4551723A (en) * | 1983-06-10 | 1985-11-05 | Sundstrand Data Control, Inc. | Excessive descent rate warning system for rotary wing aircraft |
-
1985
- 1985-12-19 CA CA000498124A patent/CA1243118A/en not_active Expired
-
1986
- 1986-02-21 WO PCT/US1986/000384 patent/WO1986005023A1/en active IP Right Grant
- 1986-02-21 EP EP86902091A patent/EP0217852B1/en not_active Expired - Lifetime
- 1986-02-21 DE DE8686902091T patent/DE3685790T2/en not_active Expired - Fee Related
- 1986-02-21 JP JP61501980A patent/JPS62500264A/en active Pending
- 1986-10-20 FI FI864239A patent/FI864239A/en not_active Application Discontinuation
-
1987
- 1987-06-12 US US07/062,368 patent/US4792799A/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| FI864239A0 (en) | 1986-10-20 |
| US4792799A (en) | 1988-12-20 |
| DE3685790T2 (en) | 1993-02-11 |
| DE3685790D1 (en) | 1992-07-30 |
| EP0217852B1 (en) | 1992-06-24 |
| FI864239A (en) | 1986-10-20 |
| EP0217852A4 (en) | 1987-07-06 |
| JPS62500264A (en) | 1987-01-29 |
| EP0217852A1 (en) | 1987-04-15 |
| WO1986005023A1 (en) | 1986-08-28 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA1243118A (en) | Aircraft terrain closure warning system with descent rate based envelope modification | |
| US4939513A (en) | System for alerting a pilot of a dangerous flight profile during low level maneuvering | |
| US5666110A (en) | Helicopter enhanced descent after take-off warning for GPWS | |
| US5283574A (en) | Altitude loss after take-off warning system utilizing time and altitude | |
| US5220322A (en) | Ground proximity warning system for use with aircraft having egraded performance | |
| EP0565660B1 (en) | Ground proximity warning instrument using flight path modulation of glide slope alerting function | |
| US5187478A (en) | Configuration responsive descent rate warning system for aircraft | |
| US3947809A (en) | Below glide slope advisory warning system for aircraft | |
| US5225829A (en) | Independent low airspeed alert | |
| GB2066759A (en) | Nagative climb after take-off warning system | |
| US4849756A (en) | Ground proximity warning system terrain classification system | |
| US4980684A (en) | Warning system for tactical rotary wing aircraft | |
| GB2148823A (en) | Excessive descent rate warning system for rotary wing aircraft | |
| WO1987004991A1 (en) | Wind shear detection and alerting system | |
| US5038141A (en) | Configuration responsive descent rate warning system for aircraft | |
| US4818992A (en) | Excessive altitude loss after take-off warning system for rotary wing aircraft | |
| US4857923A (en) | Ground proximity warning system for an excessive descent rate over undulating terrain | |
| CA1234417A (en) | System for alerting a pilot of a dangerous flight profile during low level maneuvering | |
| US4639730A (en) | Excessive terrain closure warning system | |
| US4916447A (en) | Warning system for aircraft landing with landing gear up | |
| GB2174665A (en) | Warning system for tactical aircraft | |
| AU567260B2 (en) | Excessive descent rate warning system for tactical aircraft | |
| CA1079385A (en) | Below glide slope advisory warning system for aircraft | |
| GB2140757A (en) | Excessive descent rate warning system for tactical aircraft | |
| Breen | 17.1 Enhanced Ground Proximity Warning System |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |